Commit fbac266f authored by Heiko Carstens's avatar Heiko Carstens Committed by Alexander Gordeev
Browse files

s390: select ARCH_SUPPORTS_INT128 



s390 has instructions to support 128 bit arithmetics, e.g. a 64 bit
multiply instruction with a 128 bit result. Also 128 bit integer
artithmetics are already used in s390 specific architecture code (see
e.g. read_persistent_clock64()).

Therefore select ARCH_SUPPORTS_INT128.

However limit this to clang for now, since gcc generates inefficient code,
which may lead to stack overflows, when compiling
lib/crypto/curve25519-hacl64.c which depends on ARCH_SUPPORTS_INT128. The
gcc generated functions have 6kb stack frames, compared to only 1kb of the
code generated with clang.

If the kernel is compiled with -Os library calls for __ashlti3(),
__ashrti3(), and __lshrti3() may be generated. Similar to arm64
and riscv provide assembler implementations for these functions.

Acked-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
parent 1f2597cd

arch/s390/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -117,6 +117,7 @@ config S390 
	select ARCH_SUPPORTS_ATOMIC_RMW

	select ARCH_SUPPORTS_DEBUG_PAGEALLOC

	select ARCH_SUPPORTS_HUGETLBFS

	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && CC_IS_CLANG

	select ARCH_SUPPORTS_NUMA_BALANCING

	select ARCH_SUPPORTS_PER_VMA_LOCK

	select ARCH_USE_BUILTIN_BSWAP

arch/s390/include/asm/asm-prototypes.h

+4 −0
Original line number Diff line number Diff line
@@ -6,4 +6,8 @@ 
#include <asm/fpu/api.h>

#include <asm-generic/asm-prototypes.h>



__int128_t __ashlti3(__int128_t a, int b);

__int128_t __ashrti3(__int128_t a, int b);

__int128_t __lshrti3(__int128_t a, int b);



#endif /* _ASM_S390_PROTOTYPES_H */

arch/s390/lib/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -3,7 +3,7 @@ 
# Makefile for s390-specific library files..

#



lib-y += delay.o string.o uaccess.o find.o spinlock.o

lib-y += delay.o string.o uaccess.o find.o spinlock.o tishift.o

obj-y += mem.o xor.o

lib-$(CONFIG_KPROBES) += probes.o

lib-$(CONFIG_UPROBES) += probes.o

arch/s390/lib/tishift.S

0 → 100644
+63 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */



#include <linux/linkage.h>

#include <asm/nospec-insn.h>

#include <asm/export.h>



	.section .noinstr.text, "ax"



	GEN_BR_THUNK %r14



SYM_FUNC_START(__ashlti3)

	lmg	%r0,%r1,0(%r3)

	cije	%r4,0,1f

	lhi	%r3,64

	sr	%r3,%r4

	jnh	0f

	srlg	%r3,%r1,0(%r3)

	sllg	%r0,%r0,0(%r4)

	sllg	%r1,%r1,0(%r4)

	ogr	%r0,%r3

	j	1f

0:	sllg	%r0,%r1,-64(%r4)

	lghi	%r1,0

1:	stmg	%r0,%r1,0(%r2)

	BR_EX	%r14

SYM_FUNC_END(__ashlti3)

EXPORT_SYMBOL(__ashlti3)



SYM_FUNC_START(__ashrti3)

	lmg	%r0,%r1,0(%r3)

	cije	%r4,0,1f

	lhi	%r3,64

	sr	%r3,%r4

	jnh	0f

	sllg	%r3,%r0,0(%r3)

	srlg	%r1,%r1,0(%r4)

	srag	%r0,%r0,0(%r4)

	ogr	%r1,%r3

	j	1f

0:	srag	%r1,%r0,-64(%r4)

	srag	%r0,%r0,63

1:	stmg	%r0,%r1,0(%r2)

	BR_EX	%r14

SYM_FUNC_END(__ashrti3)

EXPORT_SYMBOL(__ashrti3)



SYM_FUNC_START(__lshrti3)

	lmg	%r0,%r1,0(%r3)

	cije	%r4,0,1f

	lhi	%r3,64

	sr	%r3,%r4

	jnh	0f

	sllg	%r3,%r0,0(%r3)

	srlg	%r1,%r1,0(%r4)

	srlg	%r0,%r0,0(%r4)

	ogr	%r1,%r3

	j	1f

0:	srlg	%r1,%r0,-64(%r4)

	lghi	%r0,0

1:	stmg	%r0,%r1,0(%r2)

	BR_EX	%r14

SYM_FUNC_END(__lshrti3)

EXPORT_SYMBOL(__lshrti3)